GRB 260903A: Soft X-ray burst detected by SVOM/ECLAIRs with optical afterglow

AI Summary

SVOM/ECLAIRs detected GRB 260903A on 2026-09-03 at 12:37:20 UTC, a soft gamma-ray burst with T90 = 21 s in the 4-20 keV band and spectral properties consistent with an X-Ray Flash classification. The burst showed a single-peak light curve with fluence (1.6±0.3)×10⁻⁷ erg/cm² in the 4-120 keV range. Multiple follow-up observations confirmed an optical afterglow at RA 25.662°, Dec 11.370° with initial magnitude r ≈ 20.7 mag, fading to r ≈ 22.9 mag by 11.5 hours post-trigger. Einstein Probe detected an X-ray counterpart (9.76×10⁻¹³ erg/cm²/s), while Swift-XRT observations at T0+498 ks yielded only upper limits, indicating rapid X-ray fading.

Measurements

Notices (1)

SVOM — GRB · Thu, 03 Sep 2026 12:36:46 GMT

GCN Circulars (14)

GCN-45548 — GRB 260903A · Thu, 10 Sep 2026 14:57:05 GMT
Swift-XRT performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 260903A, finding no X-ray sources at the position of the optical afterglow. The 3-sigma upper limit for the observed flux in the 0.3-10 keV range is 8.1e-14 erg cm^-2 s^-1, with four uncatalogued sources detected too far from the GRB position to be likely afterglow candidates.

GCN-45529 — GRB 260903A · Mon, 07 Sep 2026 18:26:33 GMT
Swift has initiated a Target of Opportunity (ToO) observation of the gamma-ray burst (GRB) event GRB 260903A, detected by SVOM/ECLAIRs. Automated and manual analyses of XRT data will be conducted to identify any potential afterglow candidates, with results published online and via GCN Circulars.

GCN-45527 — GRB 260903A · Mon, 07 Sep 2026 11:59:00 GMT
The SAO RAS team observed the field of GRB 260903A using the Zeiss-1000 telescope but did not detect the optical transient. The observations were conducted on September 5, 2026, with a 3-sigma upper limit magnitude of 24.1 in the Rc band.

GCN-45519 — GRB 260903A · Fri, 04 Sep 2026 20:05:20 GMT
A team of astronomers observed the field of GRB 260903A using the Palomar 1-m telescope equipped with the WINTER camera, but did not detect the source in the J-band. They established a 5-sigma upper limit of J = 19.07 mag (AB) at the optical counterpart position.

GCN-45517 — GRB 260903A · Fri, 04 Sep 2026 17:41:50 GMT
The SVOM/ECLAIRs team reported a refined analysis of GRB 260903A, a gamma-ray burst with a single peak lightcurve and a duration of 21 seconds. The burst's spectral parameters suggest it could be classified as an X-Ray Flash (XRF).

GCN-45515 — GRB 260903A · Fri, 04 Sep 2026 15:01:32 GMT
The GRB 260903A, initially detected by the SVOM and followed by EP, was observed using the Zeiss-1000, 1-m SAO RAS telescope. The optical transient (OT) associated with the GRB was clearly detected with a magnitude of 22.45 in the Rc band, providing valuable photometric data for further analysis.

GCN-45510 — GRB 260903A · Fri, 04 Sep 2026 06:11:05 GMT
The Einstein Probe (EP) performed a follow-up observation of the gamma-ray burst GRB 260903A, detecting an uncataloged fading X-ray source within the error region identified by SVOM/VT. The X-ray source, named EPF_J014238.7+112211, has a 0.5-10 keV flux of 9.76e-13 erg/cm^2/s and a localization error radius of 10 arcsec.

GCN-45509 — GRB 260903A · Fri, 04 Sep 2026 01:52:51 GMT
The optical afterglow of GRB 260903A was detected using the T193cm telescope at Observatoire de Haute-Provence, with a preliminary magnitude of r' = 23.0 +/- 0.2 mag (AB). This detection confirms the presence of the optical counterpart reported by other observers.

GCN-45508 — GRB 260903A · Fri, 04 Sep 2026 00:54:37 GMT
The optical afterglow of GRB 260903A was observed using the Nordic Optical Telescope, showing significant fading with a magnitude of 22.88 in the SDSS r band, confirming it as the afterglow of the gamma-ray burst.

GCN-45505 — GRB 260903A · Thu, 03 Sep 2026 20:50:07 GMT
The SVOM mission team reported optical observations of GRB 260903A using the LCO telescope at Siding Spring Observatory, detecting the optical counterpart in three epochs with magnitudes ranging from 20.46 to 21.8 AB. The source showed some fading over time, but no strong evidence of variability was found.

GCN-45504 — GRB 260903A · Thu, 03 Sep 2026 19:00:22 GMT
The SVOM/VT telescope detected an uncatalogued optical source at coordinates R.A. = +01:42:38.96, Dec. = +11:22:13.73, associated with the gamma-ray burst GRB 260903A. The source was observed in both VT_B and VT_R bands with magnitudes of 21.9 +/- 0.2 mag and 20.7 +/- 0.1 mag respectively, approximately 2.1 hours after the initial trigger.

GCN-45503 — GRB 260903A · Thu, 03 Sep 2026 17:20:54 GMT
nap

GCN-45501 — GRB 260903A · Thu, 03 Sep 2026 15:11:23 GMT
nap

GCN-45499 — GRB 260903A · Thu, 03 Sep 2026 13:18:42 GMT
The SVOM mission detected a soft, faint gamma-ray burst, GRB 260903A, on September 3, 2026, at 12:37:20 UTC. The burst was localized to RA 1h42m27.28s, Dec 11d23m21.52s with a 90% confidence radius of 10.20 arcmin, but no immediate follow-up observations were performed due to low detection significance.